1. Field of the Invention
The present invention relates to an integrated circuit device reducing a noise on LSI power supply nets followed by a high speed operation. More specifically, the present invention relates to a low noise integrated circuit device including a semiconductor (e.g., CMOS), in which a power supply current flows during only a specified period of time.
2. Description of the Related Art
Followed by a high speed operation and a high integration of a semiconductor integrated circuit, a power supply current required by the integrated circuit device, particularly, simultaneous switching current, has been increasing. There is a problem that a noise occurs on LSI power supply nets, caused by resistance and inductance of power supply wiring that has to be fine to supply an electric power to the integrated circuit. Generally, a bypass condenser is used to reduce the noise on LSI power supply nets. FIG. 11 shows a noise reducing method using the bypass condenser on LSI power supply nets. An integrated circuit 110 is connected to a power supply VDD at a connection point N5 and connected to a power supply VSS at a connection point N6. An impedance 111 exists in a wiring between the power supply VDD and the connection point N5. An impedance of a wiring between the power supply VSS and the connection point N6 can be ignored because of its small value. When the integrated circuit 100 includes a logic integrated circuit with a plurality of gates that perform a simultaneous turn-on and off, a power supply current of the integrated circuit 110 has quick rise-up and down characteristics and for instance, becomes a pulse current flowing in synchronism with a clock signal. At this time, a noise L di/dt occurs dues to an inductance component of the impedance 111. Accordingly, to reduce the noise on LSI power supply nets, the power supply current is bypassed by connecting a condenser 112 between the connection points N5 and N6. Prior art relating to this kind of bypass condenser is described, for instance, in page 1166 to 1177 of IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 25, NO. 5 OCTOBER 1990.